Drawn-link electric fuse.



S. VV. HUFF.

DRAWN LINK ELECTRIC FUSE.

'APPLICATloN FILED Aua.21.1914.

1,228,924. Patented June 1917.

snauen'rnn. w. nerr, or BROOKLYN, Nnw reim.

`\ nnAwN-LINK ELECTRIC FUSE.

incassi.

Specification of Letters Patent.

Patented June 5, 1917.

Application :tiled August 21, 1914. Serial No'. 857,904.

'embodying a conducting link with relatively low fusing point and with a currentcarrying capacity below that of apparatus served by the circuit and required to be protected from the destructive effects of overloading. More specically,the inventionrelates to so-called cartridge fuses in [which the fusible link is incased to avoid damage from arcing usually incident, vtogreater or less degree, to the socalled blowing of the fuse, and in' which the link is embedded'in finely divided refractory material to dissipate the arc; and especially to larger capacityfuses of this type wherein it is very desirable to restrict the currentgaging dimension of the linkto a relatively short intermediate portion of the link so as to localize the fusing point as far as practicable from the conducting ends of the casing, and in which the remainder of the link body extending beyond the reduced portion or gaging reach, is proportioned to afford a carrying capacity that will insure against undue heating or detracting from the localizing effect of the reduced middle portion.

Heretofore it has been customary to make the links of these intermediately,v reduced fuses, of thin ribbon-like metal having its intermediate portion reduced in conducting capacity to a greater oi' less degree, as may..

be required, by notching the links inward from the edges or punching out portions thereof. But considerable diiculty and expense have generally been involved in securing uniformity of `capacity in' links of this type, owing to wide variations in the density and texture of stock metal which the market affords.I Moreover, such links are expensive to use in manufacture because of complications incident to assembling them with other parts of the fuse.

Attempts have been made to remedy these diiiiculties by theuse of bar-links of rectangular section, but with onlypartial success so far as concerns the difficulties and consequent expense of manufacture; It has been proposed to use drawn metal links in the form of round wire, but only for the smallest capacity fuses, where localizing of the fusing point and holding down temperatures in the intermediate portions is comparatively unimportant. Wire has not been used for the larger capacity fuse links, because no way has heretofore been known to satisfactorily localize the heat therein and develop an intermediate fusing point.

I have discovered that fuse links made of a drawn body of metal are particularly desirable for the larger capacities, because of uniformity of dimensions, texture and conductivity which is insured by the wiredrawing process as a method of producing the metal stock. I have also discovered by experiment that if drawn metal bodies, such as wire, having a conducting capacity suinciently in excess of the maximum current to be carried, to avoid excessive heating throughout the main body of the wire, be employed for a fuse link and an intermediate portion of such a body be reduced in section, by cutting away a portion of thel dimension transverse to the direction of drawing, the portion, of reduced transverse dimension, which remains will be of the same uniform texture and conductivity as the main lbody of metal, and can be relied upon toaiilord an accurate carr ing capacity in proportionl to the metal le in the section, so that for the purpose of accurately producing fuses of predetermined capacity,

it is merely necessary to gage the cut or reduction that is made in the transverse dimension; and this being in turn brought U under accurate control by the provision of a suitable tool whose work can be regulated at will, theproduction in large numbers of fuses uniform in gaged capacity and from metal stock purchased in the open market, can be carried on with certainty without the expense of reconditioning or re-gaging the metal. These conditions become all the more important in view of the growing demand for fuses conforming to special conditions or specifications.

The present invention will be fully understood upon reference to the accompanying drawing, in which- Figure 1 is an axial sectional view of a complete fuse constructed in accordance with the present invention and having in addition thereto a subsidiary or indicator fuse;

Fig. 2 is a view similar to Fig. 1, showing .a modification in the connections between the fusible link and the end caps of the fuse; and

Figs. 3 and 4 are sectional views showing modified forms of fuse links madeof drawn metal and having intermediate portions reduced by removal of a portion of the metal.

1 represents the case of the fuse, 2 the fusible link, 3 the end caps secured to the case by means of'pins 3, and 4l the indicator wire which has its ends lapped at la` over the ends of the case 1, so as to be brought into contact with the end caps 3, while an intermediate portion of the indicator wire extends diametrically across a bore 5 in the case 1, containing an explosive charge 6 which is backed up by the breech closure 7, preferably formed of a strip of ber cemented to theinner lface of the case, and confined on the outside by a wad 8, which may be conveniently provided from plastic material, such as plaster of Paris. The details of this indicator are not claimed in this application, but form the subject matter of a copending applicatiol Serial No. 857,903, of even date herewit l The intermediate portion of the link 2 Ais cut away so as to leave a reduced portion i 2a Whose sectional area will correspond to and accurately gage the maximum current tobe conveyed, while the main portions of the link 2 lying between the reduced portion 2a and the ends of the fuse, are of suiiicient capacity to carry4 this fusing current without undue heating. This fusible link is constructed v of a drawn body of metal and is, therefore, very accurate in dimension, texture and conductivity, so that by accurately gaging the extent of the cut at the intermediate portion, and consequently determining the transverse dimension of the reduced portion 2a that remains, the carrying capacity of the link can be determined to a nicety. Novel means are provided for securing the link 2 in the ends of the fuse. Fig. 1 shows headed sleeves or thimbles 9 introduced through central end caps, .the thimbles 9 and the ends of the' link are all firmly united by solder bodies 10 poured into the spaces between the parts as a step in the manufacture of the fuse.

According to Fig. 2, the ends of the link are secured directly in the central openings of the depressed portions 3 of the end caps by means of the solder bodies 10,

which are found in most instances sufficient to arrest the burning before it reaches the end caps. The end caps are preferably provided with the usual relief openings 3 closed by paper or other disks 11, to prevent an escape of the refractory material with which fuses of this lled.

Figs. 3 and 4 show' another method of providing a drawn metal fuse body with an intermediate portion reduced and made up of the drawn metal of uniform texture d and conductivity; the reduced portion 2 representing the original caliber of a wire forming the central portion of the link, and the increased diameter for reducing the heating effect beyond the reduced fusin point being provided by drawnl meta Jackets 2 lntlmately associated with the central core 2. The fuse link constructed in this way may be introduced into the fusev as is the link 2 in Fig. 2; or, as suggested in Fig. 4, such a composite link may be rovided with the thimbles 9 as a means o reinforcing the ends ynext to the cap in the type are usually manner already described with reference to Fig. 1.

In another aspect 'of the construction shownin Fig. 3, the jackets 2x may be regarded as prolongations of the sleeves or thimbles 9 and the may, if desired, be provided with the endv flanges with which said thimbles are shown in Figs. 1 and 4. The

sleeves 2x would, in that case2 serve the dual purpose of raising the capacity of the main portions of the link and reinforcing the link physically as well.

I claim 1. In an electric fuse, a conducting link constructed of drawn wire having an in` termediate portion cut away transversely through a portion of its thickness and therebyl reducing its dimension transverse to the direction of drawing and leaving a reduced portion of the original drawn metal with its 'structural character unchanged, corresponding in sectional area to the carrying capacity desired.

2. In an electric fuse, a link constructed of metal of round section drawn in the direction of the length of the link; the i11ter-- 1,228324 v 1 y, g

mediate portion oi said link being cut away Brooklyn, New York, this 31st day of July, f'lombthc cylindrical surfavledrinwlard and 1911i. t ere y caving a. -semi-c ica section of less transverse dimension` than the end SLAUGHTER W' -5 portions thereof, but of the same structural lIn presence ofcharacter. A y Hmmm SEGEIBACHER, The foregoing specification signed at JOHN A. Timm 

